1. Field of the Invention
The present invention relates to a workpiece regrasping system for a robot.
2. Description of the Related Art
In a configuration wherein a robot performs handling of a workpiece, there is a case, as in the orientation of a workpiece which should be gripped or held by a hand (or a workpiece orientation), where the workpiece orientation desired by the robot does not coincide with an actual workpiece orientation provided at an actual working site (such as, the orientation of the workpiece placed on a predetermined jig, or the orientation of the workpiece fed from a machine tool). For example, in an operation for picking up a workpiece by a hand and placing it on a pallet, such an inconvenience may occur that an actual workpiece orientation just before a picking-up step is different from a desired workpiece orientation on a pallet on which the workpiece is placed (e.g., the difference of a 90° orientation, between the vertical and horizontal orientations of a rectangular parallelepiped body).
In such a case, it is required for the robot to perform the handling of the workpiece (e.g., the transfer of the workpiece to the pallet) after the actual workpiece orientation is changed to the desired workpiece orientation. If the workpiece is light in weight, it is possible for the robot performing a handling operation to previously change the actual workpiece orientation to the desired workpiece orientation by the handling operation and then to pick up the workpiece placed in the desired orientation. However, if the workpiece is heavy, such as a large-sized motor or an engine component, the handling operation for changing the workpiece orientation generally applies an excessively large load to a wrist of the robot, so that it is difficult, in practice, for the robot to change the workpiece orientation. Conventionally, simple and effective countermeasures against this problem have not yet been proposed.